An associative memory is searched by content as opposed to physical location. As in other memories, the individual cells comprising the associative memory each contain one bit of information. A given number of bits form a word. In an associative search, the words in memory are compared simultaneously (in parallel) against a known search pattern which comprises a series of data bits. Any matches are detected and the physical locations of the cells containing matched data are determined. The primary advantage of an associative memory is that a search of the entire memory may be made quickly, essentially in the time that it takes to make a search of one word.
Some associative memories are limited by their design to a particular width and are not extendible by cascading memories together. Such memories thus have a maximum number of bits for a given word, i.e. 16 bits, and for such memories, search patterns longer than 16 bits cannot be searched reliably. This can be a significant disadvantage, and the applicability of such memories is correspondingly limited.
Other associative memories are designed so that they can be searched only with fixed length search patterns. This can be a disadvantage, as it is sometimes desirable to have a variable length search pattern capability.